1. Field of the Invention
The present invention relates to a ink delivery nozzle in a keyless printing press, in which ink keys provided in a doctor of an ink source roller are omitted.
2. Prior Art
One example of a keyless printing press in the prior art is shown in FIGS. 13 to 16. In FIG. 16 which shows a general construction of the keyless printing press, reference numeral 1 designates an ink reservoir, numeral 2 designates a suction pipe, numeral 3 designates a pump, numeral 4 designates a delivery pipe, numeral 5 designates a delivery nozzle, numeral 6 designates an ink feed doctor, numeral 7 designates an ink source roller, numeral 8 designates a transfer roller, numeral 9 designates a doctor roller, numeral 10 designates an anti-hysteresis doctor, numerals 11 and 12 designate ink application rollers, numeral 13 designates a wetting device, numeral 14 designates a plate drum, numeral 15 designates a blanket drum, numeral 16 designates a paper sheet to be printed, numeral 17 designates an ink feed pipe for feeding ink to the above-mentioned ink reservoir 1, and numeral 18 designates an ink circulation system. In addition, in FIGS. 13 to 15 which show details of the above-mentioned delivery nozzle 5, reference numeral 20 designates a delivery nozzle main body opposed to the above-mentioned ink source roller 7 with a minute gap clearance maintained therebetween, numeral 20 designates a cap for closing a top opening of the same delivery nozzle main body 20, numerals 22 designate inlet pipes provided at the bottom of the same delivery nozzle main body 20, numeral 23 designates a plurality of delivery ports provided in the above-mentioned cap 21, which delivery ports align along the axial direction of the ink source roller 7, and printing ink within the ink reservoir is sent under pressure into the delivery nozzle main body 20 of the delivery nozzle 5 through the route of the suction pipe 2.fwdarw. the pump 3.fwdarw. the delivery pipe 4.fwdarw. the inlet pipes 22, and the ink sent under a pressure into the delivery nozzle main body 20 is delivered and fed to the ink source roller 7 rotating at a low speed through the respective delivery ports 23. Then, the printing ink delivered and fed to the ink source roller 7 rotates and moves jointly with the ink source roller 7 towards the ink feed doctor 6, it is metered into a predetermined thickness by passing through a minute gap clearance between the ink source doctor 7 and the ink feed doctor 6, and surplus printing ink drops and returns to the ink reservoir 1. On the other hand, the printing ink having passed through the minute gap clearance between the ink sourc roller 7 and the ink feed doctor 6 is transferred to the transfer roller 8 which is rotating at a high speed while held in contact with the ink source roller 7. Subsequently, the ink is fed to the plate drum 14 through the route of the doctor roller (the doctor roller having an ink film of uniform thickness formed thereon by the anti-hysteresis doctor 10) 9.fwdarw. ink application rollers 11 and 12. In addition, at this time, wetting water is fed from the wetting device 13 to the plate drum 14. To a pattern portion of this plate drum 14 will adhere printing ink, while to a non-pattern portion will adhere wetting water, whereby a predetermined ink film image is formed. This ink film image is transferred to the sheet 16 to be printed via the blanket drum 15, and thus printing is effected.
However, the keyless printing press in the prior art as described above with reference to FIGS. 13 to 16 involves the following problems. That is, in the printing ink scraped out by the anti-hysteresis doctor 10 and dropping in the ink reservoir 1 is contained wetting water of about 20-30%, so that such wetting water enters the ink reservoir 1, in addition to fresh ink fed through an ink feed pipe 17. Since the wetting water has a smaller specific gravity than the printing ink, very fine water drops of the wetting water in the ink reservoir 1 will float up through the printing ink layer in the ink reservoir 1, will accumulate on the surface of the printing ink, and will become isolated water. This isolated water has a smaller viscosity than the printing ink, hence it more easily flows, and preferentially flows through ink circulation system 18. Even after such isolated water is delivered through the delivery nozzle 5, it will hardly adhere to the ink source roller 7 (its surface is covered by an ink film and has a strong lipophilic property) but will drop again into the ink reservoir 1. Consequently, there is the problem that the isolated water will repeatedly circulate through the ink circulation system 18 and will be successively accumulated. If such accumulation should exceed a predetermined limit, the amount of adhesion of the ink to the ink source roller 7 will become insufficient or transfer of ink to the transfer roller 8 will not be satisfactory, resulting in lowering of a printing depth.